PROJECT SUMMARY Heart failure (HF) is an enormous health burden affecting approximately 5.1 million people in the US and is the cause of 250,000 deaths each year. Approximately 50% of HF is caused by myocardial ischemia and requires immediate restoration of coronary blood flow to the affected myocardium. However, the success of reperfusion is partly limited by intramyocardial hemorrhage, which is the deposition of intravascular material into the myocardium. Hemorrhagic reperfusion injury has high prevalence and patients have a much greater risk of adverse left ventricular remodeling, risk of fatal arrhythmia, impaired systolic function and are hospitalized at a greater rate. Recent magnetic resonance imaging techniques have improved assessment of reperfusion injury, however, the association between MRI contrasts and reperfusion injury is highly unclear, and lacks specificity to IMH. Improved imaging of IMH and accurate knowledge about its spatial and temporal evolution may be essential for delivery of optimal medical therapy in patients and critical to identify patients most at risk for adverse ventricular remodeling. The overall goal is to investigate the magnetic properties of hemorrhage and develop MRI techniques with improved specificity to hemorrhage. New MRI techniques permit noninvasive assessment of the magnetic susceptibility of tissues and can target tissue iron. Therefore, we hypothesize that MRI imaging of myocardial magnetic susceptibility can map hemorrhagic myocardium. We will perform preclinical experiments in a pig model of reperfusion injury to validate these methods, compare them with conventional MR contrasts and develop MR methods for imaging live animals.